1. Field of the Invention
The present invention relates to guide catheters and method of manufacturing guide catheters. In particular, the present invention relates to an improved guide catheter unibody which resists kinking and provides better torque control.
2. Description of the Prior Art
Percutaneous transluminal angioplasty is widely accepted as an efficient and effective method for treating various obstructive disorders and vascular diseases. In particular, angioplasty is widely used for opening stenosis in coronary arteries, although it is also used for treatment of stenosis in other parts of the vascular system.
Guide catheters are well known for use in angioplasty procedures. In a typical angioplasty procedure, the guide catheter is initially inserted into an artery, such as the femoral artery or axial artery. Subsequently, the catheter is advanced transluminally to a point where the distal tip of the guide catheter is positioned within a blood vessel, near the obstructive lesion or stenosis to be treated. Alternatively, the guide catheter may be inserted preloaded, and contain a dilatation balloon and guide wire when it is initially inserted.
Next, a flexible guide wire is inserted through the lumen of the guide catheter with the distal end of the guide wire extending beyond the distal tip of the guide catheter. The guide wire is advanced, while monitored using fluoroscopy, to a point where the distal end of the guide wire is advanced past the arterial obstruction or stenosis. A dilatation balloon catheter is then inserted and advanced over the guide wire through the lumen of the guide catheter to a point where the balloon of the dilatation balloon catheter is positioned across the stenosis. The balloon is then inflated by supplying a fluid under pressure through an inflation lumen to the balloon. The balloon is inflated and deflated, pressing the lesion into the artery wall to reestablish acceptable blood flow through the artery. Upon completion of the balloon dilatation procedure, the deflated dilatation balloon catheter and guide wire are withdrawn from the patient's body using the guide catheter lumen. Lastly, the guide catheter itself is removed from the patient's body.
In angioplasty procedures, the guide catheter must be able to traverse tortuous pathways through blood vessels to the stenosis, in a manner atraumatic as possible. Therefore, to limit insertion time and discomfort to the patient, the guide catheter must be stiff enough to resist the formation of kinks, while at the same time possess flexibility to be responsive to maneuvering forces when guiding the catheter through the vascular system. It is important that the guide catheter exhibit good torque control such that manipulation of a proximal portion of the guide catheter is responsively translated to the tip or distal end of the catheter to curve and guide the guide catheter through the tortuous pathways.
In an attempt to meet the above guide catheter performance requirements, various guide catheter construction methods are used. U.S. Pat. No. 4,665,604 to Dubowik suggests a guide catheter which includes a base strand, a braided layer, and a final layer. First, the base strand is formed by extruding a material onto a wire mandril. Next, stainless steel wire is braided over the base strand to form the braided layer. Sections of the braid which will form the body of the catheter are imbedded in the base strand by passing the base strand through a heated dye. Lastly, the final coating is extruded over the braided layer.
Similarly, U.S. Pat. No. 4,321,226 to Markling suggests a method of catheter body construction which includes a first plastic layer extruded on a core wire, a wire braid applied onto the first plastic layer, and finally, a second plastic layer extruded over the wire braid. The wire braid is formed of cross-wound individual stainless steel wires.
U.S. Pat. No. 4,577,543 to Wilson suggests another similar method of catheter body construction which includes a generally cylindrical body having reinforcement material braided over the body. The body, with reinforcing strands, passes through a heated dye so that the braided strands adhere to the surface of the body. Wilson suggests that the strands may be of reinforcing material such as metal wire (steel wire) or synthetic fibers (fiberglass or aramid).
The above types of catheter construction still tend to form kinks when traversing tortuous blood vessel pathways. The braided layer lacks a tight fitting braid and evenness of joinder at the points where the wires cross in the braid. This problem results in lack of good torque control necessary for manipulation of a proximal portion of the guide catheter to impart forces at the catheter's distal end needed to curve and guide the catheter through the blood vessels.
Other guide catheter construction methods are used, which do not have a braided reinforcing layer. Such a method is suggested in U.S. Pat. No. 4,596,563 to Pande, which includes a method for making a tubular catheter having two layers. The two layers are formed of polymeric material and include a rigid inner sheath and a flexible outer sheath. The rigid inner sheath is extruded onto a mandril, and the flexible outer sheath is extruded over the rigid inner sheath. Similarly, U.S. Pat. No. 4,636,346 to Gold et al. suggests the preparation of a guide catheter having a three-layered tubular body which includes an inner sheath, a rigid intermediate sheath, and a flexible outer sheath. The rigid intermediate sheath is formed from extruding polymeric materials such as polycarbonates and polyamides over the interior sheath. Such catheters lack the structural integrity and torque response provided by a reinforcing braided layer for maneuvering the catheter through tortuous pathways of a patient's vascular system.